The present invention pertains to an electrical circuit and particularly to a circuit including a non-contacting potentiometer for providing a control signal which is proportional to the position of a detecting probe with respect to a voltage dividing impedance element
Potentiometers are typically employed for providing a control voltage or signal which varies with respect to the position of a rotary shaft to which a wiper arm is attached and which slides along a resistive element The resistive element may be a wire wound resistor or a thick-film surface formed resistor or other form of resistor capable of physical contact with the wiper arm. Although such potentiometers work well in most environments, over a period of time, their use results in some degradation of performance due to wear of the moveable element, contact surface resistance variations due to wear and/or dirt or other surface contaminants or even eventual failure. In critical applications where the position of a rotary shaft provides, for example, a vehicle control signal and where a conventional potentiometer is employed, it must be frequently inspected, maintained or even replaced.
In recent years some attempts have been made to provide a non-contacting potentiometer which eliminates the problem of surface contact resistance variations between the wiper arm and resistive element of a conventional potentiometer. Approaches have employed optical and magnetic systems for providing signals representative of the movement of one element with respect to the other, however, such systems are somewhat complicated in that they require a relatively unique sensing element which would be costly to mass produce and do not rely upon a voltage divider network to provide a control signal.